There are approximately 500,000 individuals in the United States whose vision in one or both eyes is impaired due to retinal deterioration or damage. Often, such injury primarily affects the central portion of the retina known as the macula, and results in what is commonly called central vision loss. In such cases, over 90% of the retina remains unharmed, and the peripheral vision remains intact. Such injury, however, is particularly disturbing because the macula provides acute vision, such as that needed for driving or reading. As a result, macular damage often causes an image either to appear distorted or invisible. For example, an individual with significant macular damage sees a blind spot at the center of vision and therefore is virtually unable to read printed text.
Standard eyeglass lenses commonly used to correct focusing problems are insufficient to restore proper vision to a patient suffering from macular degeneration. A variety of other previously known devices have been used to correct this problem. One such previously known device, for example, consists of telescopic systems that increase the retinal image size of an object. Such telescopic systems, however, merely increase image size, still require central vision to complete the image, and therefore, do not provide a congruent image.
To overcome problems associated with telescopic systems, other previously known devices include intricate intraocular lens systems that shift an image from a damaged to an undamaged area of the retina. For example, U.S. Pat. No. 4,581,031 to Koziol et al. (the Koziol '031 patent), describes an intraocular lens adapted to be implanted in the eye, the lens including a lens portion having a convex first portion, a second portion including a prism, and a means coupled to the lens for supporting the lens in the eye. In use, light rays strike the convex first portion, are focused, exit through the prism on the second portion and are deflected away from the macula towards and against the undiseased paracentral retinal area.
Other prior art devices include a combination of intraocular lenses and external spectacle lenses. For example, U.S. Pat. No. 4,666,446, also to Koziol et al. (the Koziol '446 patent), describes an intraocular lens adapted to be implanted in the eye and used with an external converging spectacle lens. The intraocular lens has a first portion including a diverging lens, a second portion including a converging lens, and a means coupled to the lens for supporting the lens in the eye. Use of the intraocular lens in combination with the converging spectacle lens provides a magnified retinal image of a given object, whereas use of the intraocular lens without the converging spectacle lens provides unmagnified and unrestricted peripheral vision.
U.S. Pat. No. 5,030,231 to Portney also describes an intraocular lens and a spectacle lens arrangement. The intraocular lens has a converging lens portion and a diverging lens portion that combines with multiple-element spectacles having anterior and posterior lenses arranged to converge light toward the diverging lens portion of the intraocular lens.
Other previously known lens systems are configured solely in eyeglasses. For example, U.S. Pat. No. 4,772,113 to Parker discloses eyeglasses that comprise two lens assemblies, each having a magnifying lens with two convex surfaces and a reducing lens with two concave surfaces. The reducing lens incorporates prism rings that focus an image or light onto an undamaged portion of the retina.
A disadvantage common to these and other previously known image shifting devices is that the shifted image remains fixed at one location. As a result, the eye naturally shifts the image back to the central area of the visual axis, which often is the damaged area of the macula. Also, many of these previously known devices suffer because the image appears to be distorted when viewed, or only a portion of the normal viewing area can be seen at one time.
In view of the deficiencies in previously known devices, it would be desirable to provide methods and apparatus for shifting an image from a first to a second portion of the retina while overcoming the eye's natural tendency to shift the image back to the first portion.
It further would be desirable to provide methods and apparatus for shifting an image back and forth between first and second portions of the retina.
It still further would be desirable to provide methods and apparatus for shifting an image back and forth between first and second portions of the retina at a rate sufficient to prevent the eye from shifting the image to the first portion of the retina.
It also would be desirable to provide methods and apparatus for allowing a person with macular degeneration to have an undistorted view of objects that could not previously be seen in undistorted form.